1. Field of the Invention
The present invention relates to pendent residential fire protection sprinklers, and relates more particularly to pendent residential fire protection sprinklers suitable for the protection of even relatively large residential spaces, through having the ability to provide the required coverage of even a large space with the required evenness and required throughput (flow, measured, e.g., in gallons per minute) at relatively low water pressures. The invention also relates to residential fire protection systems utilizing such sprinklers.
2. Related Art
Fire protection sprinklers conventionally are connected to a conduit to receive pressurized fire-extinguishing fluid, such as water. A typical sprinkler has a base with a threaded portion for connection to the conduit and an output orifice to output the fluid to provide fire control and/or suppression. The output orifice is sealed by a seal cap, which is held in place by a release mechanism. The release mechanism is designed to release the cap under predetermined conditions, thereby initiating the flow of fire-extinguishing fluid. A typical release mechanism includes a thermally-responsive element, e.g., a frangible bulb, and may include a latching mechanism.
Certain conventional sprinklers have a pair of arms that extend from the base portion and meet at a hub portion to form a frame. The hub portion is spaced apart from the output orifice of the base portion and lies on the longitudinal axis thereof (the axis, roughly, along which the stream of fluid flows through the orifice). The hub portion may have a set-screw configured to apply a pre-tension force to the thermally-responsive element and latching mechanism. A deflector may be mounted on the hub, transverse to the output orifice, to provide dispersion of the output fluid.
Fire protection sprinklers may be mounted on a fluid conduit running along a ceiling and may either depend downward from the conduit, which is referred to as a “pendent” configuration, or may extend upward, which is referred to as an “upright” configuration. The area to be protected may extend across an entire room, in which case the relevant fire protection standards, e.g., Underwriters' Laboratories® Standard 1626 (the substance of which is incorporated herein by reference in its entirety), require the fluid flow to reach the four walls surrounding the coverage area, and to impinge on the coverage area evenly, among other requirements. (The true application of these sprinklers having larger K-factors is for 0.1 density, per NFPA 13. NFPA 13D—one and two family dwellings (0.05 density, 2-head design for hydraulic calculation); NFPA 13R—residential occupancies up to and including 4 stories in height (0.05 density, 4-head design for hydraulic calculation); NFPA 13—residential occupancies greater than four stories in height (0.1 density, 4-head calculation); these standards, also, are incorporated herein by reference.) To provide a sprinkler that meets these requirements for residential installations is especially difficult, because the available water pressure in residences is generally below what can be utilized in a commercial space. To this end, it is desired to increase the ability of the sprinkler to deliver fluid per unit time, as a function of available water pressure. This ability is generally measured by the K factor of the sprinkler, defined as the ratio of the fluid throughput per unit time in gallons per minute, to the square root of the water pressure in gauge pounds per square inch.
In addition to achieving the ability to spray fluid at the required rate, a sprinkler must also meet certain standards pertaining to the evenness with which that fluid is delivered over the surfaces of the space being protected.
Both of these requirements make the design of a residential sprinkler a challenge. Moreover, although data has been compiled and tabulated on the characteristics of sprinklers based on K factor and the water pressure used, it is frequently found that an actual sprinkler does not perform as predicted based on the known data. Frequently, it is found that a sprinkler requires a higher-than-expected water pressure to deliver an acceptable amount of fluid per minute.
As a result, the task of designing a sprinkler having a given K factor and that not only will provide the required coverage but will do so at a particular water pressure, is a very challenging one. Depending on the particular parameters that it is desired to achieve, there is no guarantee in fact that it will actually be possible to create a design that will provide the desired level of performance.